The HC-5524 telephone Subscriber Line Interface Circuit integrates most of the BORSCHT functions on a monolithic IC. The device is manufactured in a Dielectric Isolation (DI) process and is designed for use as a 24V interface between the traditional telephone subscriber pair (Tip and Ring) and the low voltage filtering and coding/decoding functions of the line card. Together with a secondary protection diode bridge, the device will withstand 500V induced surges, in plastic packages.

Features
• DI Monolithic High Voltage Process
• Compatible with Worldwide PBX and DLC Performance Requirements
• Controlled Supply of Battery Feed Current with Programmable Current Limit
• Operates with 5V Positive Supply (VB+)
• Internal Ring Relay Driver and a Utility Relay Driver
• High Impedance Mode for Subscriber Loop
• High Temperature Alarm Output
• Low Power Consumption During Standby Functions
• Switch Hook, Ground Key, and Ring Trip Detection
• Selective Power Denial to Subscriber
• Voice Path Active During Power Denial
• On-Chip Op Amp for 2-Wire Impedance Matching

Applications
• Solid State Line Interface Circuit for PBX or Digital Loop Carrier Systems
• Hotel/Motel Switching Systems
• Direct Inward Dialing (DID) Trunks
• Voice Messaging PBXs
• 2-Wire/4-Wire, 4-Wire/2-Wire Hybrid
• Related Literature
    - AN9607, Impedance Matching Design Equations
    - AN9628, AC Voltage Gain
    - AN9608, Implementing Pulse Metering
    - AN549, The HC-5502S/4X Telephone Subscriber Line Interface Circuits (SLIC)